Alternate feed switch for firearms



E. W. HOPKINS ALTERNATE FEED SWITCH FOR FIREARMS May 20,-1952 Filed OGI.. 13,. 1949 me/Wto@ Patented May 2o, 1952 signor to the United States of America as represented by the Secretary of War Application y 2 Claims.

WamendedfApril 30, 1928;;370 0. G. 757) The invention described herein may be manufactured byor for the Government for governmental purposes without the payment of any royalty thereon. Y

This invention relates to a reversible feed mechanism fori machine guns and is directed more particularly to simplied means for alternating the direction from which cartridges are fed into a gun of the well-known Browning type. The detailed feeding mechanism of suchguns is fully described inU. S. Patent No. 1,803,351 held by Frederick L. Moore and consequently need not be here repeated in detail. However, in'order to adequately explainthe presentinlvention, it should be pointed out that the Browning type of feeding mechanismincludes a feed slide which is actuated by an elongated pivotal lever to successively advance the cartridges of a linked belt into position for extraction therefromupon recoilfof the :bolt A pair of intersecting cam grooves are formedalong the top of the bolt for selectively engaging the rear end of the pivotal lever. As the bolt recoils and counter-recoils, the lever is oscillated in accordance with the contour of thef engaged cam groove and thereby effects transverse reciprocation of the slide. Since these cam grooves intersect, vthe continuous outlines thereof are interrupted by one another at the point of intersection. Accordingly, there is provided a rotary type bolt switch having a cam track therein for completing one or the other of the cam grooves to provide a continuous path for the rear end of the belt feed lever. The direction from which the cartridges are advanced into the feedway of the gn is therefore dependent upon the particular cam groove in which the feed lever is engaged. Since the aforesaid switch must `necessarily be flush with the top surface of the bolt, a suitable circular recess is provided therein at the point of intersection of the cam grooves. Obviously, the removal of sufcient metal from the bolt to form the desired bolt switch recess detracts from the optimum endurance life of such a highly stressed member.

It is therefore an object of this invention to provide a simplified means for alternating the feed of a Browning type machine gun wherein the present rotary switch and bolt recess therefor may be eliminated.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

october-1s, 1949,:seria1 No.121,os4

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Fig. 1 is a top view of an alternate feed bolt with the switch inserts of this invention positioned for left hand feed.

Fig. 2 is a fragmentary enlarged view of Fig. 1 showing the switch inserts positioned for right hand feed.

Fig.l 3 isa cross-sectional viewtaken along the line" 3 '3 in Fig. 2.

Fig. 4 is a cross-sectional view taken through the feedway of a Browning type machine gun and Vshowing the feeding mechanism arranged for left hand feed. v

Fig. 5 `is a cross-sectional view similar to Fig. 4 but showing the arrangement for right hand feed. Fig. 6 is aV perspective view of the roll pin used lto secure the switch insert in the bolt.

Fig. 7 is a YtopA view of a Browning type machine gun with the cover removed and showing the feeding mechanism arranged for left hand feed. Y

Fig. 8 is a perspectiveview 'of the switch insert of thisinvention.

Referring now to the drawings, especially Figs. 4, 5 and 7, there is illustrated a cartridge belt feed mechanism as applied to a machine Agun of the Browning type, although it will be understood that the principles of the invention are applicableV with equal facility to any automatic weapon which is similarly fed.

As in the case of all machine guns of the Browning type, a breech bolt l0 having a cartridge extractor 28 pivotedV thereto is mounted in al Vreceiver II for reciprocable movement from and to a battery position.

'I'he cartridge belt feed mechanism comprises generally a slide I2, a belt feeding pawl I3. a belt holding pawl I4, and a belt feed lever I5. Slide l2 is arranged to reciprocate transversely of bolt I0 and feed cartridges IB of a linked belt I'I through the medium of pawl I3 in the manner well known in the art. Belt feed lever I5 is pivoted intermediate of its ends to the underside of the gun cover (not shown) and is engaged at its front end with slide I2 and at its rear end with bolt I0. Thus as bolt I0 recoils, lever l5 is pivoted to actuate slide I2 so as to engage the foremost cartridge I 6 of belt I1 and then as bolt I0 counter-recoils, lever I5 actuates slide I2 to move such cartridge along the feedway 29 of receiver Il into position to be pulled out of belt I'I by extractor 28 when the previously extracted cartridge is red.

A pair of intersecting cam grooves I8 and I9 'are formed along the top of bolt l0 and extend forward of its rear end. Grooves I8 and I9 inswitch inserts 2G to-selectivelycomplete the Iinterrupted portion'o'f cam grooves I8 and I9v in the manner illustrated in Figs. 1 and 2.

Switch inserts 2D are preferably unitary members having a trapezoidal head portion 2I and a pin-shaped body 22 extending therefrom. `Vertical holes 23 are provided in cam grooves YI8 and I9 and such holes extend sufficiently-into the'body of bolt IU to fully receive the pin-shaped body 22 of insert 20, the head portion 2| thereof being thereby arranged to lie ush with the'top of bolt I0. The distance between the parallel sides of head portion 2l is such that inserts 23 engage snugly in cam grooves I8 and IIS when assembled to bolt I0. The non-parallel sides 24 of head portions 2I areconverging-ly slopedat such angle that when inserts 29' lieincam `groove I8 or I9 on either side of the interrupted portion thereof, one Asloping side of each rhead v"portion 2I is aligned with the interrupted wall of theintersecting cam groove. Thus, as shown in Fig.-1,rswitch binserts 20 complete cam groove vIii while blocking oi the interrupted portions of ,-camfgroove I9. The converse'is true inthecase'of'the position shown --in Fig; 2.

-Asillustrated particularly well in Fig-2 and Fig. 3, holes 23 are each partially intersected by `a second hole 25v drilled transversely through'bolt IIB. lThe -latter -holes 25 eachV receive a Ysplit roll pin-25 arranged Yto engage ina circumferential groove 2 provided adjacent 'the free 'end of pinsha-perd body -22 of switch insert'20. *Since Vroll pins 263 are 'of slighl-ty larger diameter than holes 25,Vv inserts 2) are thereby Ysecurely Vkeyedl in bolt I against loosening from the shock and vibra tion of 'continuousfiring When inserts 20 are assembled tofboltf'l in the position Aindicated in Fig. "-1, the gun is adapted' to Vbe -fe'd fromthe left hand 'side (see Fig. 4). Asvbolt I0 recoils, lever I5 is pivoted so as 'to actuate slide I2 outward-ly tov-the 'left' 'and cause belt -feeding pawl iI3 to engage lthe foremost ofthe lin-kedcartridges I6. Themas-'bolt III-counter-recoils, lever I5=is pivoted toffactuate slide I-5 inwardly to thev right and y:thereby bringthe cartridge 'I6 engaged by vbelt feedi-nggpawl -I 3 int lposition to be yengaged by extractor-v 28.k

VIn the event -it is'desired to feed from the right hand side of the gun, switch` inserts-220 arev removed -from vcam groove I'Sand Vreplaced in cam groove I3 in the manner of Fig. 2. At the same time, slide I2, pawls I3 and I4 are reversed as is customary in the Browning type machine gun. The fulcrum point (not shown) of lever I5 is also changed to accommodate the reversed pivoting movement thereof and consequently the feed mechanism is thereby arranged for the right hand feed of Fig. 5.

`It can thus be readily seen that the substitution of switch inserts 20 for the previous typeof `rotary bolt switch entirely eliminates the necessity for providing a recess in the top of the bolt,

' av factor which isy highly important in increasing the endurance .life of such a highly stressed component. Moreover, the simplicity of manufacturing Ainserts Y2l! in comparison to the more complicated fabrication of the previous rotary type bolt switch introduces a significant decrease in the cost of manufacture which is always of the utmost importancein mass production.

I.I claim:

l.. In a .machine gun, a `bolt having a pair -of 1i-I-itersectir'ig cam grooves formed along the top thereof, bothof said cam grooves having Aiin-terrupted side walls lon-lyat the point of'intersec- Jtion with one another, and a pair of symmetrical members xedly secured to said bolt,said inserts being- -provided with a tra} oezoidal"head portion anda pin shaped -body portion, said Yhead portion =having a vertical thickness equivalent tothe depth of said lcam 'grooves whereby Ythe top of said .insert lies flush with the top lof said bolt, one'of the non-parallelsides of each head portion -arranged to be 'inalignmentwith 'thefside wall 'of 'that particular camgroove which' intersects' the cam groove in which said inserts aresecured whereby a continuouspathis-dened insaid :cam `groova'said pin shaped body portion` arranged Jto `extend vertically into said bolt.

2. The combination 'of r claim .1' plus: 4means 'for cooperating with said pin shaped body portion to "securely keysaid inserts in'said bolt.V

EDWARD W. Ho-PKrNs.

REFERENCES CITED The vfollowing references are of record in fthe le of this patent:

UNITED YAs'rrrrns PATENTS Number Name Date 1,803,351 Moore et al. 1May 5,l 1931 1,920,984 `Howard Aug.' '8, 1933 1,936,254 Moore .Nov.-21', T1933 -1,956,574 Hatcher May 1, 1934 

